Document Type

Technical Report

Publication Date




The purpose of the proposed research is to quantify the effects that Lakes Mead and Powell have on the salinity in the Colorado River system, and to evaluate changes that cap be made to the operating system of the reservoirs (within legal/institutional constraints) to enhance salt precipitation and/or minimize evaporation within the reservoirs. The effect of any changes (i.e., selective withdrawal uses, pumped storage, etc.) on reservoir evaporation could also be evaluated with a goal of minimizing evaporation. This will be accomplished through the development of a mathematical model of the reservoirs as described below.


Two major problems with water in the Colorado River are its quantity and its salinity. The Colorado River is an extremely regulated system, and most of the sources of salinity and depletion mechanisms have been identified, with the exception of the behavior of the large reservoirs. Lakes Powell and Mead represent a storage capacity of up to 4 years mean annual flow of the Colorado River. To date, only minimal and uncoordinated attempts have been made to systematically model the chemical and thermal storage and transfer processes in these reservoirs.

Numerous attempts have been made to roughly account for salinity in the reservoirs. Hendrick (1973) determined that the best statistical correlation between inflow and outflow in Lake Mead was a monthly complete mixing of the reservoir contents with its inflows. This had a correlation coefficient of 0.78, but treated the whole system as a black box based on historical conditions and, thus, could not predict the results of any changes in reservoir operation.

Further work, however (Reynolds, 1978), indicates that certain polyphenals inhibit the precipitation of calcite and, therefore, the actual removal of calcite from Lake Powell may be less than expected. Preliminary studies done at the E&R Center indicate that TDS (total dissolved solids) storage is increasing in Lake Powell; the true increase is somewhat masked, however, by the increase in water stored during this period and the impact of bank storage.

Evaporation also plays an important part in the Colorado River water budget as a whole and in water and TDS budgets of the reservoirs in particular. Total evaporation from Lakes Powell and Mead has been estimated at 1,300,000 acre-feet/year, or approximately 8 to 10 percent of the natural flow of the Colorado River. While there is no practical way to eliminate this loss (monomolecular films have proven totally impractical for anything but very small reservoirs), it may be possible to reduce it through a different operating scheme.


Aquatic chemistry; Colorado River (Colo.-Mexico); Effluent quality; Evaporation capacity; Lake Mead (Ariz. and Nev.); Lake Powell (Utah and Ariz.); Limnology; Salinity; Sedimentation and deposition; Water evaporation


Chemistry | Environmental Chemistry | Environmental Health and Protection | Environmental Indicators and Impact Assessment | Environmental Monitoring | Fresh Water Studies | Natural Resources and Conservation | Natural Resources Management and Policy | Sustainability | Terrestrial and Aquatic Ecology